Evaluating low impact development practices potentials for increasing flood resilience and stormwater reuse through lab-controlled bioretention systems.

Low impact development practices (LID) as alternative measures of urban drainage can be used within the approach of resources recycling and co-management. This study evaluates the potential contribution of a bioretention system to flood control, non-potable water demands (NPD) and resources co-management. Bioretention setups were tested experimentally under variable conditions to identify operational key-factors to multiple purposes. Additionally, the efficiencies obtained for laboratory scale were extrapolated for household and watershed scale, quantifying the indicators of water demand reduction (WDR), energy demand reduction (EDR) and carbon emission reduction (CER) for hybrid systems with LID. The laboratory results indicated that the use of a bioretention with a submerged zone can improve the quality of the water recovered for reuse, while maintaining the efficiency of runoff retention and peak flow attenuation. Comparing the bioretention effluent quality with the Brazilian standards for stormwater reuse, the parameters color, turbidity, E. coli and metals were above the limits, indicating the necessity of a better treatment for solids particles and disinfection. Expanding the analysis to watershed scale, the bioretention helped to reduce NPD demands up to 45%, leading to a reduction in energy demand and carbon emission from the centralized water supply system.

Bioretention performance under different rainfall regimes in subtropical conditions: A case study in São Carlos, Brazil.

Low Impact Development practices have emerged as alternative solutions for traditional urban drainage by restoring the pre-development hydrologic regime. In subtropical climate areas, the performance of these systems is still poorly understood. This study aims to assess the performance of a bioretention basin in a subtropical climate area during an entire hydrological year in order to analyze the differences between dry and rainy seasons. The main climatic factors and conditions influencing the runoff retention efficiency and peak attenuation were also analyzed in order to support bioretention design for flood control purposes. Data of 29 precipitation events were collected over three years (2016-2018). The results show that the bioretention system retained between 9% and 100% of the runoff volume with an average efficiency of 65% during a whole hydrological year. The average runoff retention efficiency was of 73% and 61% for dry and rainy seasons, respectively. This difference is explained by the climatic factors which affected the bioretention performance. During dry periods, the antecedent soil moisture condition and runoff generation rate were found to be more important than the total precipitation depth, while the runoff retention efficiency was primarily influenced by the total rainfall depth and the maximum rainfall intensity during the wet period. Future research should focus on each of these periods in more detail, including water quality aspects.